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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Sep 2022 11:15:23.5352 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 3d91397f-6fa7-4c0e-8c41-08da9c8bbe73 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: AM7EUR03FT065.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DBBPR08MB6202 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 9/19/22 13:43, Mark Brown wrote: > On Fri, Sep 16, 2022 at 01:01:31PM +0100, Catalin Marinas wrote: >> On Mon, Aug 29, 2022 at 04:49:20PM +0100, Mark Brown wrote: >>> @@ -1392,7 +1407,7 @@ static const struct user_regset aarch64_regsets[] = { >>> }, >>> [REGSET_TLS] = { >>> .core_note_type = NT_ARM_TLS, >>> - .n = 1, >>> + .n = 2, >>> .size = sizeof(void *), >>> .align = sizeof(void *), >>> .regset_get = tls_get, > >> Does this change confuse user-space? I presume an updated gdb would >> check the iov.len to figure out whether a new register is available but >> would existing debuggers complain of the new size of this regset? > > gdb seems happy as far as I can see, it is possible something would be > reusing the read_iov for repeated TLS read calls in a context where it > was only pointing at a single u64 but I'm not sure how realistic that > is given the idiom. I did do a search on sources.debian.net and didn't > turn up anything that'd have problems. > > If using this as an extensiblility mechanism is a concern we need to > bear that in mind elsewhere, and for this it's either a case of > providing another single register regset or trying to do a generic > sysreg read/get (though that'd be another regset that's not idiomatic > for the regset API). Older GDB's assume a single register for NT_ARM_TLS, so they will always fetch TPIDR. Newer GDB's will check the size and act accordingly.